1. Technical Field
The present invention relates to a substrate processing apparatus and a semiconductor device manufacturing method. The present invention is for example effectively utilized in oxidization devices, diffusion devices, annealing devices or CVD apparatus for forming an insulating film, metallic film, or semiconductor film on a semiconductor wafer (hereinafter called “wafer”) on which semiconductor integrated circuits (hereinafter called “IC”) are formed.
2. Description of Related Art
The batch type vertical hot wall CVD apparatus (hereinafter called “CVD apparatus”) is widely used in the IC manufacturing field for forming silicon nitride (Si3N4) films on multiple wafers.
Conventional CVD apparatus of this type contain the following type of processing furnace.
Namely, the processing furnace includes an inner tube that forms the processing chamber, and an outer tube is installed concentrically on the outer side of the inner tube. A manifold is installed on the bottom end of the outer tube. A nozzle for supplying gas into the bottom end of the process chamber, and an exhaust pipe connecting to the tubular space between the inner tube and the outer tube, are connected to the manifold. A heater is installed on the outer side of the outer tube. The heater heats the interior of the processing chamber to a specified temperature distribution.
During forming of a film in the processing furnace by this CVD apparatus, a boat holding multiple wafers is loaded into the processing chamber from the bottom end opening of the manifold, and a seal cap seals the bottom end opening of the manifold air-tight, and a nozzle supplies a process gas such as chlorosilane gas and ammonia gas as well as other gases into the bottom end section within the processing chamber.
The process gas supplied into the bottom end within the processing chamber, makes contact with the wafer group from below, and rises within the processing chamber while forming a film by the thermal CVO reaction, flows from the top end opening of the inner tube into the tubular space and is exhausted through an exhaust pipe connected to the bottom end section of the tubular space.
The film forming rate is dependent on the gas flow at this time, so that the film on the wafer placed at the bottom side of the boat tends to be thicker than the film on the wafer placed on the top side of the boat.
In the prior art, the control is performed so that the heater forms a temperature gradient within the processing chamber in order to eliminate this difference in film thickness among the wafers so that the film thickness among the wafers is uniform along the entire length of the boat.